Cottonseed oil oxidation catalyzed by amino acids and albumin in aqueous and nonaqueous media

Oxidation of refined cottonseed oils catalyzed by various α-amino acids and albumin has been studied in aqueous and nonaqueous media, Cysteine, phenylalanine, and albumin possessed prooxidant effect in cottonseed oil in aqueous and nonaqueous media. Serine exhibited prooxidant activity in aqueous media and minor antioxidant activity in nonaqueous media. Effectiveness of the amino acids on cotton-seed oil oxidation was in the following descending order in both aqueous and nonaqueous media: cysteine > phenylalanine > serine. The prooxidant effect in aqueous media might be due to the predominant presence of the protonated amino nitrogen, whereas amino acid-metal complex might be responsible for the prooxidant effect in nonaqueous media.     

Linoleic Acid Oxidation Catalysed by Various Amino Acids and Cupric Ions in Non-Aqueous Media

The effect of amino acids under the present investigation on linoleic acid oxidation in non-aqueous media has shown feature of an autocatalytic chain reaction and possessed minor antioxidant behaviour except cysteine. The antioxidant effect might be attributed to the absence of protonated amino nitrogen. Linoleic acid alone had an induction period of 15 hr and on the addition of various α-amino acids, the systems had an induction period ranged from 16–19 hr. This increase did not exhibit any specific function for the studied amino acids. Cysteine exceptionally possessed pro-oxidant effect and that was due to the role of HS-group. The addition of copper at concentrations of 10^?5 M and 10^?3 M to the model systems composed of linoleic acid and various α-amino acids in non-aqueous media have shown to exhibit minor and highly pro-oxidant effects respectively. The pro-oxidant effect of these amino acids in the presence of copper might be due to amino acids-copper complexes.     

Linoleic Acid Oxidation Catalysed by Various Amino Acids and Cupric Ions in Aqueous Media

Model systems were designed to study the linoleic acid oxidation in the presence and absence of various amino acids and with or without cupric ions. The tested amino acids have shown to possess potential pro-oxidant capacity in linoleic acid dispersed in aqueous media. The effectiveness of various amino acids on linoleic acid oxidation decreased in the following order: cysteine > serine > tryptophan > phenylalanine > histidine > alanine. The addition of alanine, serine, phenylalanine, histidine or tryptophan to linoleic acid have shown features of an autocatalytic oxidation chain reaction. With cysteine, there was a linear relation between concentration of hydroperoxides and time during the early stages of oxidation. The pro-oxidative activity of the tested amino acids in general could be attributed to the presence of the α-amino group in the form H₃-N-R. The apparent difference in the pro-oxidative activity is mainly due to the functional groups attached to β-carbon in the amino acid molecules. The addition of cupric ions at concentration of 10^–5 M to linoleic acid catalysed with various α-amino acids have shown that these amino acids had no significant effect. The increasing copper concentration from 10^–5 to 10^–1 M shortened the induction period of linoleic acid catalysed by amino acids having aromatic side chain, had no effect on the induction period but increased the oxidation rate during the propagation step in the model systems catalysed by alanine and serine and in the model system containing cysteine increased the linoleic acid oxidation linearly from the start of the reaction.     

Linoleic acid oxidation catalyzed by various amino acids and cupric ions in aqueous media

Model systems were designed to study linoleic acid oxidation in the presence and absence of various amino acids with or without cupric ions. The tested amino acids exhibited a potential prooxidant effect in linoleic acid dispersed in aqueous media. The effectiveness of various amino acids on linoleic acid oxidation decreased in the following order: cysteine > serine > tryptophan > phenylalanine > histidine > alanine. The addition of alanine, serine, phenylalanine, histidine, or tryptophan to linoleic acid showed an autocatalytic chain reaction. With cysteine, there was a linear relation between concentration of hydroperoxides and time during the early stages of oxidation. The prooxidative activity of the tested amino acids in general could be attributed to the presence of the a-amino group in the form H₃-N-R. The apparent difference in the prooxidative activity is mainly due to the functional groups attached in the β-carbon atom in the amino acid molecules. The addition of cupric ions at a concentration of 10^-5M to linoleic acid catalyzed with various a-amino acids showed that these amino acids had no significant effect. Increasing the copper concentration from 10^-5M to 10^-3M had the following effects: a shortening of the induction period of linoleic acid catalyzed by amino acids having an aromatic side chain, no effect on the induction period but an increase in the oxidation rate during the propagation step in the model systems catalyzed by alanine and serine, and in the model system containing cysteine a linear increase in the linoleic acid oxidation from the start of the reaction.     

Analysis of Calotropis gigantea,Acacia Caesia and Abelmoschus Ficulneus seeds

The percentage contents of oil and protein in the seeds of Calotropis gigantea Linn. (Asclepiadaceae), Acacia caesia Willd., syn. A. intsia (Leguminosae) and Abelmoschus ficulneus Wight & Arm., syn. Hibiscus ficulneus Linn. (Malvaceae) were 30.8, 8.8 and 14.4, and 19.0, 11.7 and 20.0, respectively. The major fatty acid was 18:1 in C. gigantea and 18:2 in the other two seeds oils. Malvalic, sterculic and dihydrosterculic acids were present in small quantities in A. ficulneus seed oil. The major essential amino acids in the seed proteins were phenylalanine, lysine and histidine in C. gigantea, threonine and arginine in A. caesia and lysine and phenylalanine in A. ficulneus.     

Electrochemical preparation and characterization of poly(1-amino-9,10-anthraquinone) films

Poly(1-amino-9,10-anthraquinone), PAAQ, films were prepared by electrochemical oxidation of the monomer, AAQ, in acetonitrile using LiClO₄ as supporting electrolyte. The influence of scan repetition, scan rate and monomer concentration on the formation of polymer film was studied. The electrochemical behavior of the formed polymer films was investigated in both non-aqueous and aqueous media. The prepared films were found to be more stable in organic solvents than in aqueous solutions. The investigated organic solvents are methanol, ethanol, acetone, carbon tetrachloride, benzene, and chloroform. The polymer film shows electrochemical response in both non-aqueous and aqueous media. In non-aqueous solutions it has a wide potential range of electroactivity (from −1.5 to +1.3 V). In aqueous media the polymer film shows electrochemical response in the potential range between −0.3 and +1.3 V only. The presence of quinone units suggests potential applications in diverse areas such as electrocatalytic processes and lithium ion batteries.     

The use of modified divinylbenzene-polystyrene resins in the separation of fermentation products. A case study utilizing amino acids and a dipeptide

The adsorption of phenylalanine, aspartic acid, asparagine and aspartame from phosphate-buffered aqueous solutions with modified divinyl-benzene-polystyrene resins has been investigated using high pressure liquid chromatography (HPLC). The pH studied was 2.8, the temperature range was 293-313 K and the ionic strength was maintained at 1.0 mol dm^?3. Over the range of variables investigated, the adsorption isotherms are linear and may be characterized by temperature and pH-dependent apparent adsorption equilibrium constants, characteristic of the resin-adsorbate system. By studying the dependence on temperature of this adsorption constant, heats of adsorption and entropy of adsorption have been estimated. In terms of the heat liberated on adsorption, the amino acids and a dipeptide can be ranked thus: aspartame > phenylalanine > aspartic acid > asparagine.     

Removal of amino acids from water by adsorption on polystyrene resins

The adsorption of eight amino acids, L ‐asparagine, D,L ‐threonine, L ‐lysine, L ‐leucine D,L ‐methionine, L ‐tyrosine, L ‐phenylalanine and D,L ‐tryptophan, on the non‐polar macroporous adsorbents Amberlite XAD‐2 and XAD‐4 (polystyrene–divinylbenzene copolymers) was studied. Equilibrium adsorption experiments were conducted to estimate the types of isotherm and their parameters. The effect the chemical composition and structure of the amino acids on the efficiency of adsorption was evaluated. The influence of pH and ionic strength was also studied. The data of adsorption isotherms of the examined amino acids seemed generally to approach the Freundlich isotherm model. Tryptophan isotherm adsorption data could match in some cases the Langmuir model. The majority of the adsorption isotherms were almost linear. In terms of adsorbed amino acid on both resin surfaces, the amino acids can be ranked thus: D,L ‐tryptophan > L ‐phenylalanine > D,L ‐methionine, L ‐tyrosine > L ‐leucine > L ‐lysine > D,L ‐threonine > L ‐asparagine. In low pH solution, adsorption was generally higher than that at intermediate and high pH values. Generally, as the ionic strength increases, the adsorption of the amino acids increases. © 2001 Society of Chemical Industry     

Antioxidant activity of amino acid sodium and potassium salts in vegetable oils at frying temperatures

Previous studies reported that several amino acids had strong antioxidant activity in vegetable oils under frying conditions. In this study, amino acids were converted to their sodium or potassium salts, and a heating study was conducted with 5.5 mM amino acid salts in soybean oil (SBO) at 180°C. Sodium salts of amino acids including alanine, phenylalanine, and proline and disodium glutamate had significantly stronger antioxidant activity than the corresponding amino acids, and potassium salts had stronger antioxidant activity than sodium salts. Potassium salts of alanine and phenylalanine more effectively retained tocopherols in SBO than the corresponding amino acids during heating. Phenylalanine potassium salt had stronger antioxidant activity than phenylalanine in other vegetable oils including olive, high oleic soybean, canola, avocado, and corn oils. Phenylalanine potassium salt at 5.5 mM more effectively prevented oil oxidation than tert-butyl hydroquinone, a synthetic antioxidant, at its legal concentration limit (0.02%) indicating its feasibility as a new antioxidant for frying.     

Comportement electrochimique anodique de divers neuroleptiques en milieu aqueux et non-aqueux

The electrochemical properties of a number of neuroleptics structurally related, with a piperazinyl side chain associated to a tricyclic ring system in aqueous and non-aqueous media have been examined by voltammetry at rotating platinum, vitreous carbon and carbon paste disc electrodes, cyclic voltammetry and controlled potential coulometry.In neutral aqueous and non-aqueous media an irreversible oxidation is observed for the three compounds, probably giving rise to polymeric structures disturbing the electrochemical analysis.In non-aqueous media, in the presence of two equivalents of perchloric acid per molecule, the piperazinyl group is protonated and no oxidation peaks are observed. Only the clozapine molecule biprotonated remains oxidizable but at a more anodic potential, the behavior is then the same as in aqueous acidic media; the oxidation is located on the tricyclic ring. The results observed are confirmed by infra-red(ir), uv visible, and mass spectrometric techniques.     

Oxidation of Amino Acids,Peptides and Proteins by Ozone: A Review

The kinetics and products of the reaction of ozone with specific amino acids, peptides, and proteins are reviewed based on studies reported in the literature. Ozone reacts mainly with the unprotonated amino group of the acids and the second-order ozone rate constants for these reactions, except for cysteine, methionine, and tryptophan, vary by about two-orders from 2.6?×?10⁴ to 4.4?×?10⁶ M^?1s^?1. The site of attack on cysteine and methionine by O₃ is at the sulfhydryl rather than the amino group to give sequential O-atom addition products. The order of reactivity for the oxidation of amino acids by O₃ at pH 8 is cysteine > tryptophan ≈ methionine > phenylalanine ≈ histidine > others, with half-lives mostly in the range of milliseconds to tens of seconds (1 mg L^-1 O₃ dose). Reactions of O₃ with aliphatic amino acids form nitrate, ammonia, and one or two carbon atom-containing carbonyl and carboxylic byproducts. In the ozonolysis of peptides and proteins, oxidation by O₃ occurs at the tyrosine, tryptophan, histidine, cysteine, and methionine residues. Oxidation of proteins results in changes in their folding ability and tertiary structures.     

Characterization of proteins in Cuphea (PSR23) seeds

This study characterized the proteins in Cuphea (PSR23) seed to provide fundamental information on their size, amino acid profile, solubility classes, and solubility behavior. The seed contained 32% (dry basis, db) oil and 21% (db) crude protein. Over 70% of the protein was extracted at pH 11.6. Nonprotein nitrogen accounted for 9% of the total N content. Compared with the Food and Agriculture Organization/World Health Organization/United Nations University suggested pattern of requirements, Cuphea PSR23 seed protein had sufficient amounts of methionine+cystine-cysteine, considerable amounts (90%) of valine, phenylalanine+tyrosine, but was practically devoid of tryptophan. Lysine was the second-most limiting essential amino acid at 68%. Glutelins and albumins accounted for 83.5 and 15.4%, respectively, of the total protein extracted. SDS-PAGE showed that Cuphea protein subunits had M.W. ranging from <6.5 to 110 kDa. Dominant protein subunits in albumins had M.W. of 30, 40, 50, and 86 kDa. Glutelins had two major protein subunits with M.W. of 15 and 30 kDa. The distribution of essential amino acids was better in the albumin and glutelin fractions than in the defatted meal.     

Microwave heating to prevent deterioration of cottonseed during storage

Fuzzy cottonseed samples of 14.5% moisture and <1.0% free fatty acids (FFA) contents heated in a conventional, home-style microwave oven at 700W and 2450 MHz for intervals up to 2.0 min. The 2.0-min treatment reduced the moisture content to 13.1%. Examination of the seed immediately after microwave heating (MWH) indicated no differences in the proteins or in the quality or quantity of the cotton linters as compared with unheated seed. Neither the oil content of the seed nor the quality of the oil were affected by the microwave treatment. After nine weeks of storage at 50°C, the unheated seed had a FFA content of >3.0% while the FFA content of the 2.0-min microwave-heated seed remained <1.0%. During this storage period there was significant deterioration of the protein quality of the unheated seed. The 2.0-min MWH treatment, however, maintained the integrity of the protein during storage.     

Effect of nitrogen and zinc fertilization and plant growth retardants on cottonseed, protein, oil yields, and oil properties

The increase in the population in Egypt makes it imperative to explore promising approaches to increase food supply, including protein and oil, to meet the needs of the Egyptian people. Cotton is the principal crop of Egyptian agriculture. It is grown mainly for its fiber, but cottonseed products are also of economic importance. Cottonseed is presently the main source of edible oil and meal for livestock in Egypt. Field experiments were conducted in two successive seasons at the Agricultural Research Center (Giza, Egypt) on cotton (Gossypium barbadense L. cv. Giza 75) to determine the effect of nitrogen (N) fertilizer rate (107 and 161 kg of N/ha applied as ammonium nitrate containing 33.5% N in two equal doses at 6 and 8 wk after sowing), together with foliar applications of plant growth retardants (mepiquat chloride “Pix”, chloromequat chloride “Cycocel”, and daminozide “Alar”, each applied once at 288 g active ingredient/ha, after 75 d from sowing) and zinc (Zn) (applied in chelated form after 80 and 95 d from sowing at 48 g of Zn/ha) on seed, protein and oil yields and oil properties of cotton. The higher N-rate, as well as the application of all growth retardants and Zn, resulted in an increase in cottonseed yield, seed protein content, oil and protein yields/ha, seed oil refractive index, unsaponifiable matter, and total unsaturated fatty acids (oleic and linoleic). These treatments tended to decrease oil acid value, saponification value, and total saturated fatty acids. The seed oil content tended to decrease as N-rate increased and increased with the application of all growth retardants and Zn. There were some differences between Pix, Cycocel, and Alar regarding their effects on the studied characters. The highest increase in seed, oil, and protein yields/ha was found with Pix, followed by Cycocel. The Cycocel treatment gave the lowest total saturated fatty acids oil content, followed by Alar.     

Inhibitory Effect of Amino Acids and Dipeptides on the Sensitized Photooxidation of Fats

The protective effect of amino acids and dipeptides on the singlet molecular oxygen photo-oxidation of soybean oil and thier FAME was investigated, in homogeneous media and in aqueous emulsions. Soybean oil was chosen as an example of fat due to its particular stability problem. In the presence of 10–100 ppm of the amino acids, photo-oxidation of the fats in relatively concentrated solutions, was considerably retarded when exposed to visible light, with an added sensitizer. The study indicates that amino acids and peptides, could acd as protective agents against fats photo-oxidation, specially in foods containing oxidizable non saturated fatty acids, constituted in many cases by emulsions, where fats can simultaneously be disolved with proteineaceous compounds.     

Recognition of amino acids by membrane potential and circular dichroism of immobilized albumin membranes

The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α-helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.     

Effects of membrane fatty acid composition on sodium-independent phenylalanine transport in Ehrlich cells

We have examined Na⁺-independent phenylalanine transport in Ehrlich cells having different degrees of membrane fatty acid saturation. These differences were produced by growing the cells in mice fed a fat-free chow supplemented with either sunflower seed oil or coconut oil. Plasma membranes isolated from the cells grown on sunflower oil were enriched with polyenoic fatty acid, especially 18∶2, whereas those isolated from the cells grown on coconut oil were enriched in monoenoic fatty acids, primarily 16∶1 and 18∶1. Arrhenius plots of phenylalanine uptake showed two transitions. The temperatures of these transitions were different in the two cell preparations; 17 C and 24 C for the cells enriched in polyenoic fatty acids, 19 C and 28 C for those enriched in monoenoic fatty acids. Therefore, this transport system is sensitive to changes in the fatty acid composition of the lipid phase in which it operates. The activation energies, however, were the same in both cell preparations; 14, 8 and 4 kcal/mol. There also was no significant effect of the lipid modifications on either the K′_m or V′_max of this transport process. The K′_m for phenylalanine uptake from a choline medium remained constant as the temperature was raised from 17 C to 37 C, whereas the V′_max showed about a two-fold increase in both cell types. Phenylalanine exodus from the cells into an amino acid-free suspending medium, analyzed using first-order kinetics, also was not influenced by these membrane fatty acid modifications. The changes in the transition temperatures probably reflect differences in the degree of fatty acid unsaturation of lipids that surround and interact with the phenylalanine carrier. Such differences, however, do not appreciably influence the catalytic activity of this transport system.     

Effect of some amino acids on the rate of dissolution of calcite crystals in aqueous systems

The dissolution of calcite seed crystals has been investigated in the presence of some amino acids by constant composition method in which the undersaturation and ionic strength were maintained constant. The crystal dissolution rates are markedly inhibited by the addition of amino acids. The order of the degree of inhibition is L-arginine > glycine > phenyl alanine > alanine. Application to a kinetic Langmuir-type model suggests that adsorption of the amino acids at the active dissolution sites is the cause of the reduction in the dissolution rates.     

Synthesis of Carbonated Cotton Seed Oil and Its Application as Lubricating Base Oil

Epoxidized cotton seed oil (ECSO) was conveniently synthesized from cotton seed oil (CSO) in the presence of hydrogen peroxide, formic acid, and phosphoric acid. Then the ECSO was converted into carbonated cotton seed oil (CCSO) by reacting with CO₂ using tetrabutylammonium bromide as a catalyst. The reaction conditions including reaction temperature, pressure, reaction time and the amount of catalyst were examined. In addition, the final product (CCSO) from cyclic addition reaction was characterized by FT-IR, ¹H NMR and TGA. Compared with CSO and ECSO, CCSO showed excellent thermal and oxidation stability. Additionally, the CCSO’s properties of extreme pressure, anti-wear and friction reduction were tested and analyzed. The results indicated that it could be used as potential lubricating base oil.     

Effect of randomization on the oxidative stability of corn oil

Randomized corn oil TAG oxidized much faster than natural oil, but after purification with alumina, they oxidized at the same rate. We showed that this effect could not be attributed to a difference, in total tocopherols in the randomized and natural oils. Polar material recovered from the alumina treatment was fractionated by TLC, and a pro-oxidant effect was found in the fractions containing MAG and DAG. However, MAG and DAG, although mild pro-oxidant could not account for the pro-oxidant effect generated by randomization. No other compounds could be detected in the MAG fraction by MS. The pro-oxidant effect of randomized oil disappeared when EDTA or citric acid was added in sufficient amounts. The pro-oxidant effect of randomized corn oil was increased by the incorporation of additional copper or iron at a concentration that did not catalyze oxidation of the purified oil. Treatment of corn oil with ascorbic acid, ascorbyl-6-palmitate, ethyl acetoacetate, ethyl diacetoacetate, and acetylacetone did not reproduce the effect of the unknown pro-oxidant. Although the identity of the pro-oxidant is still unknown, we have confirmed that it is produced during randomization; it does not have pro-oxidant activity alone, but it facilitates the catalytic activity of the transition metal ions.